The purpose of this Core is to provide support to Center investigators for the structural and quantitative analysis of cyclooxygenase metabolites. The Core will provide state-of-the-art sensitive and specific assay methodology based on capillary column gas chromatography/electron capture negative ion chemical ionization mass spectrometry for quantitative analyses. Structural analyses will be carried out on one of the nine mass spectrometers that are available in the Core. Confirmation of structures will involve the use of NMR spectroscopy (if possible) and total synthesis of novel metabolites. In addition to using existing methods we propose to develop new methods for eicosanoid analysis based on capillary HPLC in combination with electrospray mass spectrometry. It is anticipated that this will provide a new powerful way to carry out quantitative analyses. In addition, we propose to explore the use of a new four-sector tandem mass spectrometer for carrying out the structural elucidation of novel eicosanoids. Of particular interest will be the coupling of high resolution electrospray ionization with the high energy collision regime that is available on the four sector instrument. Samples will be introduced into the electrospray source using an ABI-based capillary HPLC system that was recently constructed in our laboratory. The instrumentation used in these studies will also be available to individual investigators should they want to carry out their own analyses. Investigators will be trained in the operation of instrumentation by the mass spectrometry engineer. Advice on the use of appropriate ionization techniques and column selection will be provided by personnel in the Core. The Core will also provide a resource for the synthesis of eicosanoid metabolites and stable isotope standards for use in stable isotope dilution assays.